Lovers' heartbeats and respiration patterns tend to synchronize when the partners are simply in each other's presence. But what does the role of touch play in this synchronization, and what happens when one of the partners is experiencing pain?
Have you ever noticed that when you walk alongside your partner, your steps tend to synchronize? Or that when you speak to a close friend, you tend to adopt the same posture as them?
The scientific name for this is "behavioral synchrony," and it refers to the human ability to synch up with other people for the sake of living in a society.
Some studies have shown that people are not only able to synchronize their behavior, but that they can also sync up their physiology.
"Interpersonal synchronization" can manifest in various ways. For example, when people watch the same movie, their brain activity synchronizes. Similarly, when lovers stare into each other's eyes, their hearts quite literally beat
The team was led by Pavel Goldstein, a postdoctoral pain researcher in the Cognitive and Affective Neuroscience Lab at CU Boulder, and the findings were published in the journal Scientific Reports.
Dr. Goldstein explains what prompted his research, saying, "My wife was in pain, and all I could think was, 'What can I do to help her?' I reached for her hand and it seemed to help. I wanted to test it out in the lab: can one really decrease pain with touch, and if so, how?"
Studying pain and touch in couples
Dr. Goldstein and colleagues gathered 22 heterosexual couples for their study, who were all aged between 23 and 32.
The researchers asked the couples to participate in a range of tests that replicated the experience of being in a delivery room.
The female participants were assigned the role of "pain receiver," while the men were "pain observers."
Dr. Goldstein and team recorded the participants' respiration rates and heartbeats using an electrocardiogram under both pain and no pain conditions, as well as in both touch and no touch conditions.
Under the no pain condition, the couples either sat together without touching, sat together while holding hands, or were in separate rooms. In the pain scenario, all three situations were repeated, but the woman was subjected to "mild heat pain" for 2 minutes.
Touch restores synchronicity, eases pain
The study confirmed previous findings and showed that couples do synchronize physiologically just by being in each other's company.
When the woman was subjected to pain and her partner did not touch her, that physiological coupling was considerably diminished. However, when the male partner held her hand, heart rates and respiration rates synched up again, and the woman's pain was reduced. Additionally, holding hands increased the male partner's empathy.
Overall, touch seems to play a key role in interpersonal synchronization, as it increased physiological coupling regardless of whether the woman was in pain or not.
This confirms Dr. Goldstein's previous research, in which he showed that the more empathetic a man is toward a woman, the less pain the woman feels.
It appears that the more physiologically synched we are, the more our pain subsides. However, the researchers do not know whether lower-intensity pain increases interpersonal synchronicity, or whether it is the other way around.
"It could be that touch is a tool for communicating empathy, resulting in an analgesic, or pain-killing, effect," Dr. Goldstein says. Interpersonal coupling may also enhance the analgesic effects of touch using the autonomic nervous system, the authors hypothesize.
Dr. Goldstein also supposes that interpersonal synchronization may affect a brain region called the anterior cingulate cortex, which has been associated with decision-making, social interactions, pain perception both in oneself and in others, and empathy.
But more research is needed, he concedes, to understand the precise mechanism by which a partner's touch helps to diminish pain.
Limitations of the study include the fact that it did not examine same-sex couples or the effect of touch on men experiencing pain.